P. flavescens) is a medium-sized member of the Percid family, native to northeastern USA and eastern and central Canada. It inhabits cool to warm water lakes, ponds and slow-flowing rivers. P. flavescens...

Summary of Invasiveness

P. flavescens) is a medium-sized member of the Percid family, native to northeastern USA and eastern and central Canada. It inhabits cool to warm water lakes, ponds and slow-flowing rivers. P. flavescens is resilient to a wide range of environmental conditions and can survive in waters with low dissolved oxygen, low pH and high salinity. Its adaptability and wide range of environmental tolerances have led it to become a successful, established, invasive species outside of its native range. The species has been introduced in reservoirs and lakes in the Pacific Northwest and British Columbia, Canada, for sport fishing since the 1980s. P. flavescens is a voracious benthivore and can shift the balance in a benthic invertebrate community and reduce native fish numbers in small lakes due to its prey consumption. It may also have a negative impact on Pacific salmon migration and recruitment, as it shares a habitat with and predates on young salmon. The species comprises an important fishery in the Great Lakes and Chesapeake Bay. Sought after for both commercial and recreational fishing, overfishing and declining water quality have resulted in a drastic drop in fish recruitment and fishery landings of P. flavescens. Management of its native stocks must be coupled with efforts to reduce its illegal spread and control its non-native expansion.

Description

P. flavescens is a laterally compressed oblong fish with a distinct yellow to golden-yellow colour. It has 6-8 dark vertical stripes along either side, a green/olive back and a white belly. The lower fins tend to be yellow or red on adult males especially during spawning. The lateral line is curved with 51-61 scales and has a rough texture due to its characteristic ctenoid scales. This small to medium sized percid has an average size of 10.0-25.5 cm, with a maximum reported length of 50 cm in older specimens. The broad range of average length is due to the fact that populations vary in size from location to location. P. flavescens has two dorsal fins (with marked separation from one another), a frontal-spiny fin with 12-14 spines and a rear-soft fin with 12-13 soft rays and 2-3 spines.

Distribution

P. flavescens is native to Canada and the USA. The species’ range extends east of the Rocky Mountains in Canada, from Alberta to Nova Scotia (Brown et al., 2009; USGS NAS., 2015). In the USA its native range extends from the Dakotas eastward to Maine and along the eastern seaboard southward to Georgia (Brown et al., 2009; USGS NAS, 2015).

USGS NAS (2015) suggested that P. flavescens’ presence in Florida, Georgia and Alabama is likely not due to introduction, but to the fact that these areas are part of its native range. The authors refer to some samples collected in the 1850s, before any stocking took place. For more detailed information consult USGS NAS (2015).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

The expansion of P. flavescens outside of its native range is due to its intentional introduction and stocking for sport fishing (Roberge et al., 2001), as well as further human-driven spread, such as bait bucket contamination (USGS NAS, 2015). Stocking of the species began in the late 19th century (Brown et al., 2009; DFO, 2011). In 1891 the first successful introduction in California took place, when 6000 specimens brought over from Illinois were placed in Lake Cuyamaca and Feather River (Dill and Cordone, 1997). Further introductions in California, as well as population transplantation, followed the initial stocking in that state. Similar stocking episodes took place along the Pacific Northwest of the USA, with stocking programs driven by the US Fish Commission (Brown et al., 2009). The species has been stocked in Washington, Utah, Oregon, New Mexico and Texas (Roberge et al., 2001).

P. flavescens has also been introduced via illegal stocking, which together with range expansion may be responsible for the extensive spread of the species west of the Rockies in British Columbia (Roberge et al., 2001; Brown et al., 2009).

P. flavescens was found in an undisclosed lake in the Kinai Peninsula, Alaska (Fay, 2002). This population was extirpated with rotenone by the Alaska Department of Fish and Game (Fay, 2002).

Risk of Introduction

Introduction of P. flavescens has been due to intentional legal and illegal stocking and the subsequent spread of the species through interconnected watersheds, as well as human-driven bait bucket contamination. Further spread of the species into uninvaded reservoirs or watersheds can be avoided by reducing the amount of illegal stocking and the species’ use as bait. P. flavescens is adapted to a wide range of environmental conditions and habitat types and can therefore colonize uninvaded areas with ease (Roberge et al., 2001).

Habitat

P. flavescens naturally inhabits warm to cool lakes, ponds, slow flowing rivers and brackish to saline waters. The species is most abundant in clear water lakes and ponds near vegetation, and less abundant in rivers and streams, where it is mostly found in pools and areas resembling lentic habitats. P. flavescens inhabits a wide geographic range in North America, encompassing an array of different habitats, due to its tolerance to many environmental conditions. The species exhibits a high tolerance for low oxygen levels as well as acidification and is known to survive winterkill (due to lack of dissolved oxygen). P. flavescens remains near the shore, between 1-10 m deep and close to vegetation. Turbid water bodies with high concentrations of suspended sediments are usually avoided, as sediment adheres to the surface of fertilised eggs, reducing the rate of inwards oxygen-diffusion and resulting in delayed hatching.

Biology and Ecology

A study comparing the mitochondrial DNA control region sequence in P. flavescens specimens across its native range, conducted by Sepulveda-Villet et al. (2009), showed low genetic variation within the species. The most marked genetic separation was between two population sets, one inhabiting the Great Lakes, Lake Winnipeg and the upper Mississippi river watersheds, and the second inhabiting the Atlantic and Gulf Coasts together with Lake Champlain. These two watersheds separated around 365,000 years ago. Genetic separation in watersheds concurs well with the geographical separation of populations (Sepulveda-Villet et al., 2009).

Reproductive Biology

Spawning takes place in the spring months (April/May), when water temperatures range between 7 and 11°C (Williamson et al., 1997; Animal Diversity Web, 2000). The fish spawns in shallow waters in lakes or slow moving sections of rivers, such as tributaries (Williamson et al., 1997; Roberge et al., 2001; Brown et al., 2009;). Sexual maturity of males is reached during their third year, whereas females reach maturity about a year later (MDNR, 2015b). Literature values of spawning depth for P. flavescens range from 0-13 m, but the majority of values are concentrated in the shallower range of depths above 3 m (Brown et al., 2009).

Male P. flavescens are the first to arrive at the spawning ground, with two to five accompanying a single female while she lays her eggs (Roberge et al., 2001; Brown et al., 2009). The female proceeds to deposit her egg mass, followed by the release of milt from up to two of the males, a process which takes five seconds. Thereafter the females immediately retreat from the spawning ground while the males remain for a short period of time (Brown et al., 2009).

No nest is prepared for the eggs, which are laid over sand or gravel substrates, in areas of dense rooted vegetation cover, with fallen trees and brush (Roberge et al., 2001; MDNR, 2015b). An average of 23,000 eggs are laid per female, which rapidly swell and harden after deposition (Animal Diversity Web, 2000). The eggs are deposited in a jelly-like buoyant spiral that adheres to vegetation and moves in the water column, increasing aeration of the eggs (Roberge et al., 2001; Brown et al., 2009). Hatching occurs 8-10 days after spawning (releasing fry 4-7 mm in length), after which the yolk is consumed during a period of five days followed by rapid growth of the young-of-the-year (Animal Diversity Web, 2000; Roberge et al., 2001; Brown et al., 2009).

Longevity

P. flavescens has a relatively short lifespan, living no more than 7 to 8 years (Williamson et al., 1997; Animal Diversity Web, 2000).

Activity Patterns

P. flavescens is active during daylight hours. At daybreak it forms spindle-shaped schools of 50 to 200 similar sized fish (Mecozzi, 2008). The formation of schools is reportedly a mechanism to overcome their poor swimming ability and inability to accelerate quickly (Animal Diversity Web, 2000; Brown et al., 2009). Some older fish can be found traveling alone, not forming part of a school (Animal Diversity Web, 2000). When feeding, the schools concentrate near the bottom and thereafter can be found at varying depths (Mecozzi, 2008). Darkness drives the yellow perch closer to shore, and once the fish can no longer see each other the school dispersers and individuals move to the bottom to overnight, remaining motionless (Mecozzi, 2008).

The spawning of P. flavescens during spring brings them towards the shore, or upstream to calmer waters. This is followed by their return to deeper waters as water temperatures rise in the summer months (Piavis, 1991; Mecozzi, 2008). There is no evidence to suggest that P. flavescens undergoes migrations not related to its spawning behaviour. Piavis (1991) suggested that adult perch remain in the river systems in which they were born. Juvenile migration downstream from spawning locations has not been reported to be a synchronized migration event (Piavis, 1991).

Nutrition

The dietary composition and behaviour of P. flavescens changes markedly with fish developmental stage and exhibits strong monthly variations depending on prey species availability/community composition. From the larval stage to adulthood the feeding behaviour of P. flavescens will shift from planktivorous through benthivorous to piscivorous (even cannibalistic) (Iles and Rasmussen, 2005; Brown et al., 2009). Larval diet is mainly composed of zooplankton species, varying in species composition with location (Brown et al., 2009). In eastern US reservoirs, larval perch consumed copepods and cladocerans along with species of Diaptomus and Diaphanosoma (Brown et al., 2009). In Oregon, larvae have been reported to also prey on Daphnia (Brown et al., 2009).

P. flavescens increases in size with age and shifts towards bottom feeding, focusing mostly on benthic macrofauna (Brown et al., 2009). One year old yellow perch, in Lake Opinicon in Ontario, still fed on cladocerans, but most of their diet was composed of benthic Amphipoda, Ostracoda, Isopoda, Ephemeroptera, Zygoptera, Anysoptera and Chironomid larvae (Keast, 1977). Fish consumption began in second year-class specimens, with most of the consumption nearing the end of the summer (Keast, 1977). Keast (1977) observed that after their third year, P. flavescens had completely excluded cladocerans from their diet and the fraction of fish consumed became more pronounced.

In Lake Erie during 1981, the dietary composition of P. flavescens ranged in size from 50 to 200 mm and varied considerably between summer/autumn months (Schaeffer and Margraf, 1986). The same authors observed that P. flavescens specimens mostly fed on cladocerans, copepods and chironimids in June and July, and slowly shifted to larger prey in August, consuming considerable numbers of fish (Notropis sp., Dorosoma cepedianum and Morone americana). During September, Schaeffer and Margraf (1986) reported an even broader range of prey, with about 25% of prey volume cladocerans. The study did not discriminate specimens by age, merely by size.

Because of the large fraction of benthic macroinvertebrates in the fish’s diet, its livelihood heavily relies on the health of the zoobenthic community. Heavy metal contamination in lakes near industrial areas decreases the diversity of the benthic community, shifting the balance towards metal-tolerant species (Iles and Rasmussen, 2005). Benthivorous perch in metal-contaminated lakes have been observed to exhibit slowed growth and the fish community usually shifts its feeding behaviour to accommodate for the lack of benthic prey (Iles and Rasmussen, 2005).

Impact Summary

Economic Impact

The P. flavescens commercial and recreational fisheries are of great economic importance in the Great Lakes (Brown et al., 2009) and in Chesapeake Bay (Piavis, 1991). The perch’s widespread distribution and abundance led to it becoming an important commercial fishery in the USA and Canada (el-Zarka, 1959). The P. flavescens commercial fishery encompasses Lakes Erie, Huron and Michigan (Animal Diversity Web, 2000).

Commercial fish landings of P. flavescens have declined since their peak in stocks in the mid-twentieth century. Peak harvests in Lake Erie occurred during the early 1930s, the 1950s and early 1970s (Sepulveda-Villet et al., 2009). In 1954 the commercial P. flavescens fishery provided over 16 million tons of fish, comprising over 13% of all lake fish harvest (el-Zarka, 1959). In 1969 Lake Erie experienced its peak in commercial P. flavescens catch, at 13,546 tons (Animal Diversity Web, 2000). By 1976 the commercial catch had dropped to 3,175 tons, due to overfishing and water quality issues related to increased concentrations of organic compounds and higher phosphorous loadings (Sepulveda-Villet et al., 2009). Continued overexploitation, recruitment failure, introductions of exotic species and fluctuating phosphorus concentrations led to the stock’s continuous decline into the 2000s (Sepulveda-Villet et al., 2009). In 1990 the Lake Michigan commercial fishery collapsed and has not yet recovered (Sepulveda-Villet et al., 2009).

A similar chain of events was observed in the Chesapeake Bay fishery, where harvests fell from over one million pounds at the turn of the twentieth century to annual catches of a little over 40,000 pounds in the 1990s (Piavis, 1991). The annual fishing income of a P. flavescens fisherman in Chesapeake Bay was estimated at around $20,000 (USD) in 1990 (Piavis, 1991).

Despite the decrease in landings and the precipitous fish stock decline the P. flavescens fishery still plays an important economic role. In 2002 a total landing of over 3,600 tons in Canada was valued at over $16 million (CAD), and the fish remains the most valuable commercial catch in Ontario.

Environmental Impact

Introduced P. flavescens directly impact zooplankton, benthic and fish communities, due to the changing diet along P. flavescens’ life history. Introduced P. flavescens had a direct impact on the zooplankton community of the Phillips Reservoir in Oregon (Shrader, 2000). Shrader (2000) observed a rapid and abrupt increase of 245% in P. flavescens numbers in the reservoir only four years after it was first detected there. Monitoring of zooplankton populations and gamefish showed a reduction in numbers of members of the zooplankton community, predated on by perch, as well as abrupt declines in black crappie (Pomoxis nigromaculatus) and smallmouth bass (Micropterus dolomieu) densities (Shrader, 2000). Shrader (2000) observed declines in calanoid copepod and Daphnia numbers, which fell from 15 and 39% of the zooplankton community to 2 and 24%, respectively. Non-prey zooplankton organisms increased in density during the observation period. The consumption of prey by P. flavescens shifted the structure of the zooplankton community, as well as the size distribution of member-organisms (Brown et al., 2009). It is unlikely that these effects translate to larger water bodies. Observations in Lake Washington indicated that P. flavescens zooplankton consumption made up only about 2% of annual zooplankton production (Brown et al., 2009).

Changes in the size and structure of the benthic community were observed in Little Minnow Lake, Ontario, after the introduction and population increase of P. flavescens (Post and Cucin, 1984). The same authors documented a 60% reduction in total benthic biomass and a 50% reduction in mean weights over a two year period in the littoral zone. Nevertheless, less marked effects have been observed in larger water bodies. Cobb and Watzin (1998) examined the effects of P. flavescens predation on the benthic community in the littoral zone of Lake Champlain. The study concluded that only moderate changes in the community structure were observed under high perch-density trials. Instead of the top-down control Cobb and Watzin (1998) expected, they observed a bottom-up control, where the abundance of benthic prey influenced the growth rates of P. flavescens. Similar evidence was presented by Luek et al. (2010): the fish has difficulties proliferating in acidified lakes, despite its high tolerance for acidity, because of the low abundance of benthic prey.

Non-indigenous piscivorous fish in the Pacific Northwest are thought to affect Pacific salmon recruitment (Sanderson et al., 2009). Bonar et al. (2005) observed that P. flavescens does in fact consume coho salmon (Oncorhynchus kisutch), but that it did not comprise a significant fraction of the total predation. In Lake Sammamish, P. flavescens were observed to consume salmonid smolts, with 40-50% of the perch’s diet consisting of chinook salmon (Oncorhynchus tshawytscha) smolts (Brown et al., 2009). Because of the large numbers of P. flavescens in the Pacific Northwest, it could pose a threat to chinook migration and recruitment (Brown et al., 2009).

Social Impact

P. flavescens is sought after in Canada and the USA for sport fishing (Brown et al., 2009). The fish is easy to catch (Piavis, 1991) and its white meat is considered very good to eat (Brown et al., 2009). Piavis (1991), estimating that the willingness of a fisherman to pay $0.50 (USD) to catch a P. flavescens in Maryland, gave a hypothetical sport-fishery value for P. flavescens of $120,000 in the state of Maryland.

Human food and beverage

Similarities to Other Species/Conditions

Sander vitreus (walleye) is a similar looking species of percid that also has two separate dorsal fins (MDNR, 2015b). S. vitreus is noticeably larger than P. flavescens and does not have the latter’s characteristic dark stripes on the sides (MDNR, 2015a). S. vitreus can also be distinguished from P. flavescens by its fan-like canine teeth (MDNR, 2015a), which are absent in P. flavescens.

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Eradication

The piscicide rotenone was successfully used in Alaska to eradicate a P. flavescens population in a lake in the Kenai Peninsula (Fay, 2002).

Control

In small water bodies, in the absence of predatory fish, P. flavescens tends overcrowd and stunt (Shrader, 2000; Mecozzi, 2008; Brown et al., 2009). Stunted perch are unattractive for sport fishing and population controls need to be implemented to reduce perch numbers, which will lead to an increase in fish size (Mecozzi, 2008). The stocking of walleye (Sander vitreus) or other predatory fish is common practice for decreasing perch densities in overpopulated lakes (Mecozzi, 2008).

Post JR; Cucin D, 1984. Changes in the benthic community of a small precambrian lake following the introduction of yellow perch, Perca flavescens. Canadian Journal of Fisheries and Aquatic Sciences, 41(10):1496-1501.

Roberge M; Slaney T; Minns C, 2001. Life History Characteristics of Freshwater Fishes Occurring in British Columbia, With Major Emphasis on Lake Habitat Characteristics. Canadian Manuscript Reports of Fisheries and Aquatic Sciences, 2574:189 pp.